Systems and methods to reduce sensor interference associated with electrical therapies

ABSTRACT

A method of reducing stimulation signal interference with an electrical monitoring device includes sensing an electrical interference signal at a first location in a body resulting from delivery of an electrical muscle stimulation signal at a second location in the body, and delivering an electrical counter signal to the patient that destructively interferes with the electrical interference signal to prevent interference with the electrical monitoring device.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.16/104,658, filed Aug. 17, 2018, which is a Divisional of U.S.application Ser. No. 14/769,511, filed Aug. 21, 2015, which is a 371U.S. National Application of International Application No.PCT/US2014/024435, filed Mar. 12, 2014, which claims the benefit of andpriority to U.S. Provisional Application No. 61/801,002, filed Mar. 15,2013, all of which are hereby incorporated by reference herein in theirentireties.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference.

BACKGROUND OF THE INVENTION

Neuromuscular electrical stimulation (NMES) (also referred to as poweredmuscle stimulation, functional muscle stimulation, electrical musclestimulation, electrical stimulation, and other terms) is an establishedtechnology with many therapeutic uses, including pain relief, preventionor retardation of disuse atrophy, and improvement of local bloodcirculation. NMES is typically delivered as an intermittent andrepeating series of short electrical pulses. In many implementations,these pulses are delivered transcutaneously by surface electrodes thatare attached to a person's skin. Electrodes may be held to the skinthrough the use of straps, adhesives, or other mechanisms, and oftencontain a coupling layer composed of hydrogel that is capable ofenhancing the efficiency of energy transfer from the electrode to theskin and underlying tissues.

A group of persons who could potentially show large benefit from NMEStherapy are those who are being monitored medically for other conditionsor as a standard part of their medical care. For example, many patientsin the hospital are subjected to long periods of bed rest and developatrophy that NMES could prevent. During hospitalization these patientsare often connected to cardiac and other electrical monitors (ex. ECG)that measure/track certain aspects of the patient's health (for example,assessing potential arrhythmia and calculating heart rate). Similarstatements may be made about subjects who might use NMES in otherclinical settings or at home—electrical monitoring is often an importantpart of a patient's care that may drive either diagnostics or anintervention. Monitoring equipment may be external and temporary (ex.Holier monitor) or may be part of an implanted device that is permanentor semi-permanent. Monitoring and sensing capabilities may bestand-alone or integrated into another piece of medical equipment ordevice.

As NMES delivers electrical impulses to the body during its therapeuticapplication, there is the potential for interference with electricalmonitoring equipment. For example, electrical signals delivered to thebody as part of NMES treatment may be detected by sensors associatedwith other equipment, even in areas of the body remote to the site ofNMES application. These NMES signals may alter or combine with (forexample, through constructive or destructive interference) thephysiological signals the sensors are intended to measure. If ofsufficient amplitude, this interference may mask or alter signalsdetected by sensors in such a way that these signals are no longerreflective of the physiological event intended to be monitored.Accordingly, dangerous conditions may arise where a critical clinicalevent is not detected (for example, a cardiac arrhythmia goesundetected) or a device that implements sensing/monitoring behaves in anundesired fashion (for example, an implanted defibrillator shocks thepatient during normal cardiac function because sensor interference isinterpreted as a critical arrhythmia).

It is important to distinguish the situation currently described fromthe case of external electrical noise or other forms of external noiseinterfering with sensors. Sources of potential monitor interferencearising from outside of the body are well-understood, and appropriatemechanisms are well-known in the art to prevent or limit substantialdeleterious effects associated with these sources of noise. Thepresently-described situation, where sensor/monitor interference arisesdue to an electrical signal injected into or otherwise applied to thebody, is much more challenging to handle and has limited availablesolutions.

The prior art illustrates some attempts to solve the interferenceproblem described herein, but solutions described have inherentpractical limitations. Solutions described in the prior art often usehardware or software-based signal filters that are applied to noisy datacollected by sensors. Depending on the characteristics of both thedesired and the interfering signals, these filters may be successful atremoving the interference signal or minimizing its impact, allowingmonitors and devices to function normally. Other solutions known in theart involve the use of additional sensors that are used in conjunctionwith the primary sensors associated with the monitor or device. Theseadditional sensors may detect the interference signal, or a differentcombination of the desired and interference signals, and can be combinedwith data from the primary sensors in order to eliminate or minimize theimpact of the interference signal on monitoring or sensing. For example,some systems described in the art use secondary sensors to measure theinterference signal applied to the body, then subtract secondary sensordata from primary sensor data (which measures a combination of thedesired physiological signal and the interference signal applied to thebody) to minimize residual interference. Similar systems combinesignals, sometimes from many additional sensors, in different ways (withor without the use of signal filters) to achieve similar goals.

The prior art systems noted above have practical limitations related totheir implementation in the real-world. For example, to use filteringtechniques to limit the impact of interference signals applied to thebody, one would need access to sensor data following its detection butbefore it is interpreted, displayed, or otherwise used byalgorithms/components later in a monitoring or device system's process.As a result, filters can be employed by the original manufacturers ofmonitoring equipment, but third-parties trying to prevent interferencewith existing equipment/monitors/sensors are prevented from implementingnew filters as they generally do not have the proper access to makehardware or software modifications to existing equipment. Similarlimitations are associated with a multiple-sensor approach; even incases where the use of multiple sensors could help eliminateinterference with measurements of physiological signals, these sensorscannot generally be added post-market to existing monitors or devicesthat measure and interpret data.

As one specific example, take the case of a patient in a hospital havinghis cardiac signals monitored with standard ECG equipment. ECG signalsare measured by sensors (ECG electrodes) applied to the body and relayedto a processor/display unit via conventional leads that are well-known.If NMES is applied to the patient, signals detected by ECG electrodesmay be a blend of the cardiac signals desired to be measured and aninterference electrical signal produced as a byproduct of NMEStreatment. Even if the NMES interference signal could be isolated andmeasured exactly with secondary sensors, there is no way to adjust theECG electrode data with information from the secondary sensors withoutmajor modifications to the ECG monitoring system. In other words, theECG sensor data is ported directly to the processer/display unit, andthere is no practical way to intercept this data and adjust it usinginformation from a secondary sensor before it is interpreted anddisplayed. Similar limitations are associated with the use of the filterapproach. Thus, there is no way to prevent this type of signalinterference using these methods without working directly with the ECGmonitor manufacturer to implement them. As there are a vast possibilityof devices and monitors that could suffer from interference from NMESdevices and other devices that supply electrical signals to the body,collaborating with each manufacturer to implement to the techniquesdescribed in the prior art is impractical and thus these solutionsaren't feasible for widespread use.

Novel solutions are needed to allow NMES and other devices to be usedsafely in the presence of monitoring and sensing equipment. These newapproaches must solve the practical problems described above, and allowfor interference reduction to be implemented in such a way that nomodifications to monitoring devices are needed in order to reduce theinterference produced by the therapy devices and subsequently detectedby the sensors on the monitoring devices. Disclosed within are devices,systems, and methods for achieving these goals.

SUMMARY OF THE INVENTION

Detailed within are devices, systems, and methods for reducing theinterference that electrically-based systems or therapies may produce inmonitoring systems or devices that involve sensing electrical signals.Several embodiments and implementations of the invention are describedherein, though it will be evident to those skilled in the art that theseare exemplary and that numerous configurations of the present inventionare possible. An important aspect of many of the embodiments of thepresent invention is that interference is reduced by preventing orlimiting interference signals from reaching primary sensors associatedwith monitoring system or device sensors. As opposed to methods andsystems described in the prior art, which use filters or secondarysensors to try to remove interference components from a combinationsignal (comprised of both desired and interference signal components)detected by primary sensors, the present invention seeks to preventthese interference components from reaching the primary sensor in thefirst place. Accordingly, no modifications of existing monitoringsystems or devices is required in order to reduce or eliminate theimpact of interference signals on the ability for these systems ordevices to measure their target physiological signals. While much ofthis disclosure is written using the modality of NMES as an illustrativeexample, it will be obvious to those skilled in the art that with minormodifications the methods, devices, and systems described herein may beapplied with utility to other energy-delivery therapies as well.Similarly, while interference with ECG monitoring will be used as anexample, this should not be construed as limiting as the same inventionsmay be applied to minimize interference with other types of monitoringand/or devices. It should be appreciated that different aspects of theinvention can be appreciated individually, collectively, or incombination with each other.

In a preferable embodiment, an NMES system is configured with multipleindependent energy-delivery channels. One or more of these channels isused to apply NMES therapy to a body part. A by-product of thisapplication of NMES energy is an interference signal that could inhibitthe function of devices elsewhere on or in the body that monitor orsense electrical signals. To address this problem, other channels in theNMES system may be used to provide a counter signal which can interactand destructively interfere with the interference signal produced by thestandard NMES waveforms. This counter signal has an amplitude and aphase such that, at monitoring locations remote to the site of NMEStherapy, the interference signal produced by NMES energy delivery iseliminated or minimized. Some embodiments may have more energy channelsdedicated to apply NMES to a body part than energy channels used tocancel the NMES interference signal remotely. This active cancellationapproach is differentiated from the prior art because interferencesignals are addressed prior to them reaching the primary sensorassociated with monitoring devices or other equipment—no alterationsneed to be made to existing equipment.

In preferable embodiments of the invention, the amplitude, phase, shape,and other properties of the counter signal may be adjusted by a user toachieve optimal results. In variation embodiments, the counter signal isfixed or adjusted automatically based on settings of the NMES device. Inpreferable embodiments, the electrodes used to deliver the countersignal to the body are located in a fixed location relative to thestimulation electrodes used to deliver NMES energy to the body. Invariations of the preferable embodiments, the electrodes delivering thecounter electrode signals may have adjustable locations relative to theregion of NMES therapy.

In a variation of the preferable embodiment, sensors are integrated intothe NMES system that measure the interference signals produced by theNMES treatment. In some embodiments, this measurement occurs remotelyfrom the region being treated with NMES, while in some embodiments thesensing/measurement occurs locally. After sensors have measured thesignal produced by NMES, internal systems are used to adjust andfine-tune the counter signals that are produced by the system in orderto limit or eliminate interference with monitoring equipment or sensingdevices.

In some embodiments, multiple independent energy delivery channels areused to produce the counter signal. In this embodiment, each independentenergy channel may be configured to deliver energy to separate pairs orgroups of electrodes, so that the counter signal may take on numerousshapes and properties. In other variations of a preferable embodiment, asingle energy delivery channel interfacing with a single pair ofskin-contact electrodes is used to provide to the counter signal to thebody. In further variations, a monopolar configuration is implementedthat uses a single electrode contact site to provide the desired countersignal.

An important aspect of preferable embodiments of the invention is thatenergy delivered to produce the counter signal does not interfere withor degrade the ability to successfully treat a patient or subject withNMES. In other words, the counter signal can effectively cancel the NMESinterference signal at remote sensing locations but does not degrade theNMES electrical signal used to create muscle contraction in the regionbeing treated with NMES. Any viable solution to the problems describedherein must allow both the NMES system (or another energy-relatedtherapy that is being applied) and the monitoring/sensing system to beused normally and effectively simultaneously.

The disclosed devices, methods, and systems are useful because they willenable effective NMES therapy in a subset of persons that currently maynot qualify for it due to reliance on monitoring systems or devices. Forexample, the United States FDA currently requires device labeling forNMES systems indicating that they should not be used on patients withcardiac pacemakers or defibrillators, as there is a fear of theconsequences of interference with the sensing systems in these devices.Novel devices, systems, and methods that could prevent interference withthe sensing systems of cardiac devices would allow NMES therapy to reacha much larger group of patients who could benefit from the treatment.The presently-disclosed inventions will also allow NMES to be used moresafely in hospital settings, particularly those settings which requirepatients to be connected to ECG or other monitoring systemscontinuously.

One aspect of the disclosure is a muscle stimulation system comprising astimulation electrode configured to be secured to a patient to deliveran electrical muscle stimulation signal to the patient; and an countersignal electrode configured to be secured to the patient and relative tothe stimulation electrode to deliver an electrical counter signal to thepatient; and at least one controller adapted to generate the electricalmuscle stimulation signal and the counter signal, wherein the electricalcounter signal is adapted to destructively interfere with an electricalinterference signal resulting from the electrical muscle stimulationsignal.

In some embodiments the electrical counter signal is adapted such thatit does not degrade the stimulating effect of the electrical musclestimulation signal.

In some embodiments the electrical counter signal is adapted to minimizeor eliminate the interference signal.

In some embodiments the electrical counter signal has an oppositepolarity and substantially the same amplitude as the interferencesignal.

In some embodiments the electrical counter signal has an amplitude thatis less than an amplitude of the electrical muscle stimulation signal.

In some embodiments the electrical counter signal has a shape that isdifferent than a shape of the electrical muscle stimulation signal.

In some embodiments the at least one controller is adapted so that theelectrical counter signal is fixed.

In some embodiments the at least one controller is adapted such that theelectrical counter signal can be manually or automatically varied. Theat least one controller can be adapted such that at least one of anamplitude, a phase, and a shape of the electrical counter signal can bemanually or automatically varied. The at least one controller can beadapted to vary the electrical counter signal based on the electricalinterference signal. The system can further include an interferencesignal sensor configured to be secured to the patient and to sense theelectrical interference signal.

In some embodiments the system also includes an interference sensorconfigured to be secured to the patient and adapted to sense theinterference signal at a location different than where the electricalmuscle stimulation signal is delivered to the patient, wherein theelectrical counter signal is based on the sensed interference signal.

In some embodiments the electrical counter signal is adapted to reduceinterference between a sensed physiological signal from the patient andthe interference signal. The physiological signal from the patient canbe an EKG signal.

In some embodiments the system further comprises a pad configured to bepositioned on the patient and comprises the stimulation electrode andthe counter signal electrode. The pad can further comprise aninterference sensor adapted to sense the electrical interference signal.The interference sensor can be disposed between the stimulationelectrode and the counter electrode. The counter electrode can bedisposed between the stimulation electrode and the interference sensor.

One aspect of the disclosure is a method of reducing interference in amuscle stimulation system comprising delivering an electrical musclestimulation signal to a patient to stimulate muscle contraction; anddelivering an electrical counter signal to the patient thatdestructively interferes with an interference signal resulting fromdelivering the electrical muscle stimulation signal.

In some embodiments delivering the electrical counter signal does notdegrade the stimulating effect of the delivered electrical musclestimulation signal.

In some embodiments delivering the electrical counter signal minimizesor eliminates the interference signal.

In some embodiments delivering the electrical counter signal comprisesdelivering an electrical counter signal that has an opposite polarityand substantially the same amplitude as the interference signal.Delivering the electrical counter signal can include delivering anelectrical counter signal that has an amplitude less than an amplitudeof the delivered electrical stimulation signal.

In some embodiments delivering the electrical counter signal comprisesdelivering an electrical counter signal that has a shape that isdifferent than a shape of the electrical muscle stimulation signal.

In some embodiments the method further comprises modifying a parameterof the delivered electrical counter signal and delivering a secondelectrical counter signal with the modified parameter. Modifying aparameter of the delivered electrical counter signal can includemodifying at least one of an amplitude, a phase, and a shape of thedelivered electrical counter signal. Modifying a parameter of thedelivered electrical counter signal can be in response to sensing theinterference signal with an interference signal sensor.

In some embodiments the method further comprises sensing theinterference signal with an interference signal sensor. Sensing theinterference signal with an interference signal sensor can comprisesensing the interference signal at a location different than where themuscle stimulation signal is delivered to the patient and where thecounter signal is delivered to the patient. Sensing the interferencesignal with an interference signal sensor can comprise sensing theinterference signal at a location between where the muscle stimulationsignal is delivered to the patient and where the counter signal isdelivered to the patient.

In some embodiments delivering an electrical counter signal is inresponse to sensing the interference signal.

In some embodiments the method further comprises sensing a physiologicalsignal from the patient, and wherein delivering the counter signalreduces interference between the sensed physiological signal and theinterference signal. Sensing a physiological signal from the patient cancomprise sensing an EKG signal from the patient, and delivering thecounter signal can reduce interference between the EKG signal and theinterference signal.

One aspect of the disclosure is a therapeutic energy delivery systemcomprising a therapeutic energy delivery element configured to besecured to a patient to deliver therapeutic energy to the patient; acounter energy delivery element configured to be secured to the patientand relative to the therapeutic energy element to deliver counter energyto the patient; and at least one controller adapted to generate thetherapeutic energy and the counter energy, wherein the counter energy isadapted to destructively interfere with interference energy resultingfrom the therapeutic energy.

In some embodiments the counter energy is adapted such that it does notdegrade the therapeutic effect of the therapeutic energy.

In some embodiments the counter energy is adapted to minimize oreliminate the interference energy.

In some embodiments the therapeutic energy is an electrical signal, thecounter energy is an electrical signal, and the interference energy isan electrical signal. The counter signal can have an opposite polarityand substantially the same amplitude as the interference signal. Thecounter signal can have an amplitude that is less than an amplitude ofthe therapeutic signal. The counter signal can have a shape that isdifferent than a shape of the therapeutic signal. The at least onecontroller can be adapted such that at least one of an amplitude, aphase, and a shape of the counter signal can be manually orautomatically varied. The at least one controller can be adapted to varythe counter signal based on the interference signal.

In some embodiments the at least one controller is adapted such that thecounter energy can be manually or automatically varied.

In some embodiments the system further comprises an interference sensorconfigured to be secured to the patient and adapted to sense theinterference energy at a location different than where the therapeuticenergy is delivered to the patient, wherein the counter energy is basedon the sensed interference energy.

In some embodiments the counter energy is adapted to reduce interferencebetween sensed physiological energy from the patient and theinterference energy. The sensed physiological energy from the patientcan be an EKG signal. The system can further include a sensor adapted tobe secured to the patient at a location relative the therapeutic energyelement and configured to sense the physiological energy from thepatient.

One aspect of the disclosure is a method of reducing interference in atherapeutic energy delivery system comprising delivering an electricaltherapeutic signal to a patient to provide a therapeutic benefit to thepatient; and delivering an electrical counter signal to the patient thatdestructively interferes with an electrical interference signalresulting from delivering the electrical therapeutic signal.

In some embodiments delivering the electrical counter signal does notdegrade the therapeutic effect of the delivered electrical therapeuticsignal.

In some embodiments delivering the electrical counter signal minimizesor eliminates the interference signal.

In some embodiments delivering the electrical counter signal comprisesdelivering an electrical counter signal that has an opposite polarityand substantially the same amplitude as the interference signal.Delivering the electrical counter signal can comprise delivering anelectrical counter signal that has an amplitude less than an amplitudeof the delivered electrical therapeutic signal.

In some embodiments delivering the electrical counter signal comprisesdelivering an electrical counter signal that has a shape that isdifferent than a shape of the electrical therapeutic signal.

In some embodiments the method further comprises modifying a parameterof the delivered electrical counter signal and delivering a secondelectrical counter signal with the modified parameter. Modifying aparameter of the delivered electrical counter signal can comprisemodifying at least one of an amplitude, a phase, and a shape of thedelivered electrical counter signal. Modifying a parameter of thedelivered electrical counter signal can be in response to sensing theinterference signal with an interference signal sensor.

In some embodiments the method further comprises sensing theinterference signal with an interference signal sensor. Delivering anelectrical counter signal can be in response to sensing the interferencesignal. Sensing the interference signal with an interference signalsensor can comprise sensing the interference signal at a locationdifferent than where the therapeutic signal is delivered to the patientand where the counter signal is delivered to the patient. Sensing theinterference signal with an interference signal sensor can comprisesensing the interference signal at a location between where thetherapeutic signal is delivered to the patient and where the countersignal is delivered to the patient.

In some embodiments the method further comprises sensing a physiologicalsignal from the patient, and wherein delivering the counter signalreduces interference between the sensed physiological signal and theinterference signal. Sensing a physiological signal from the patient cancomprise sensing an EKG signal from the patient, and delivering thecounter signal reduces interference between the EKG signal and theinterference signal.

BRIEF SUMMARY OF THE DRAWINGS

As shown in FIGS. 1A-1B, an embodiment of the systems and devicesdescribed herein that demonstrates the main system components.

As shown in FIGS. 2A-2D, variations of preferable embodiments of thedevices and systems that include electrodes used to deliver NMES andelectrodes used to produce a counter signal.

As shown in FIGS. 3A-3E, various electrical signals associated with thedevices, systems, and methods described herein.

As shown in FIGS. 4A-4E, variations of preferable embodiments of thedevices and systems that include electrodes used to deliver NMES andelectrodes used to produce a counter signal as well as sensors used inconjunction with the system.

As shown in FIGS. 5A-5B, variation embodiments of the devices andsystems shown in multiple configurations.

As shown in FIG. 6 , several steps in one preferable embodiment of themethod described herein.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides methods, devices, and systems for limiting theimpact electrical-based therapies may have on monitoring systems and/orother devices that require sensing of electrical signals. Though thisdisclosure uses the modality of NMES as an illustrative example, thoseskilled in the art will appreciate that the presently-disclosedinvention may be applied with utility to other energy-delivery therapiesas well. Various aspects of the invention described herein may beapplied to any of the particular applications set forth below or for anyother types of electrical stimulation and sensing systems or methods.The invention may be applied as a standalone device, or as part of anintegrated medical treatment system. It shall be understood thatdifferent aspects of the invention can be appreciated individually,collectively, or in combination with each other.

With reference to FIGS. 1A-1B, in a preferable embodiment, the systemincludes three core components: surface electrodes that are used tocouple electrical energy into and out of the body (104, 105), astimulation control unit (101) that creates the stimulation energy andpotentially other electrical pulses and delivers them to the surfaceelectrodes, and a wired connection (102) to allow communication betweenthe electrodes and control unit. In some variation embodiments, awireless system using may be used that eliminates the need for a wiredconnection, instead using a radiofrequency transmission, optical,acoustic, or electromagnetic signals, or another suitable mechanism. Ina preferable embodiment, the electrodes will be assembled into a custompad (103) such that electrode layout and configuration will bepre-optimized for a particular region of the body. Some electrodes maybe pre-designated to deliver stimulation energy that delivers NMEStherapy (104), while others may be configured to produce counter signals(105) intended to prevent the NMES therapy from creating meaningfulinterference in remote sensors that are intended to measureelectrophysiological signals. In some embodiments, electrodes may beused both to deliver NMES therapy and to deliver counter signals, and/ormay be designated by the user or control unit to produce one type ofsignal or the other at the time of NMES treatment. The control unit is aseparate unit that may be located some distance from the personreceiving therapy. In an alternate embodiment, the control unit may beintegrated into a housing unit containing the stimulating electrodes, orin another way be adapted to reside proximate to the region of NMES.

In a preferable embodiment, the control unit contains components such asa signal generator, memory, processor, and power supply. The primaryoperation of the control unit may be provided by a microprocessor, fieldprogrammable gate array (FPGA), application specific integrated circuit,some combination of these mechanisms, or other suitable mechanism.Electrical transformers or another suitable mechanism is used to produceelectrical energy pulses that may be delivered to the body of a subject.When activated, the control unit generates electrical signals that aretransmitted to the surface electrodes in the pad, which couple theenergy into the body (for example, to activate muscles). Some electricalstimulation parameters, including the duration of therapy, areadjustable by the operator through buttons, knobs, dials, or switches onthe control unit. Other electrical stimulation parameters, such asstimulation pulse energy amplitude, may be adjusted by the user throughcontrol unit controls or be automatically optimized using automaticalgorithms implemented by the control unit. The control unit may alsocontain items such as a touchscreen or other form of display and/or userinterface, data acquisition channels and associated hardware/software,and other safety-control features.

In a preferable embodiment, the control unit is capable of transmittingelectrical pulses on at least one and preferably many more (ex. 6-12)channels simultaneously and independently. In some embodiments, thecontrol unit may also be capable of creating arbitrary phase delaysbetween pulses originating from different channels. In variations ofthese embodiments, the control unit may transmit pulses on some channelsdependently and others on different channels independently.

In a preferable embodiment, the system electrodes are arranged on a padin an array with a predetermined layout (see, for example, FIG. 1B). Ina preferable embodiment, the pads are comprised of a thin and flexiblehousing with an adhesive backing to facilitate maintenance of skincontact with the person receiving NMES. More than one adhesive materialmay be used; for example electrode contact areas may use a hydrogel orsimilar backing while other pad areas may be secured with a more gentleadhesive (ex. those used in bandages). The hydrogel backing forelectrodes will also enhance the coupling of electrical energy andsignals between stimulation electrodes and the person's body. The padcontains two or more strategically-placed surface electrodes that areused to deliver electrical energy to muscles and/or nerves in order toproduce muscle contraction, as well as one or more electrodes used toproduce a counter signal. In variation embodiments, electrodes may bediscretely-placed in contact with tissue independent of a larger pad (asin FIG. 2D). In some embodiments, a system pad may also contain a smalland lightweight control unit that is intended to sit proximate to theregion of tissue being treated. In some embodiments, more than one padmay be used, with each pad containing at least one electrode thatproduces either a stimulating or counter signal.

In preferable embodiments the system will be configured specifically fora particular region of the body intended to receive NMES. Referring toFIG. 2A, a system is shown configured for use with muscle stimulation ofthe left quadriceps. A control unit (202) is shown to connect to a padcontaining electrodes (203) through a wired connection. Also shown arecommon locations for ECG electrodes (204) which are used to monitor thesubject's cardiac activity. In preferable embodiments of the system,electrodes used to deliver the counter signal to the body will liebetween the monitoring system sensors and the electrodes used to deliverNMES therapy. In the example shown, the counter-signal electrodes thuslie between the quadriceps and the torso. In FIG. 2B, a detailed view ofone embodiment of a system pad (203) is shown, with example locations ofstimulation electrodes (2044) and electrodes used to deliver the countersignal (205). Note the counter signal electrodes would fall between theNMES electrodes and the ECG measuring electrodes of the monitoringsystem. A different implementation of this embodiment is shown in FIG.2C, where the counter signal electrodes are arranged differentlyrelative to the stimulation electrodes, primarily because the pad (206)has been configured to deliver therapy to a different anatomicallocation (for example, the back). In FIG. 2D, an embodiment of thesystem is shown where no pad is used; both types of electrodes areplaced discretely on the skin at locations of the operator's choosing,and are not fixed in position relative to one another.

During the process of NMES, electrical energy is generally deliveredbetween at least two electrodes in a set. The bulk of electrical energytravels between the electrodes in the set, though fields of energyspread away from the stimulation region. It is these fields which cancreate interference problems for monitoring in remote regions. Examplesare provided in FIGS. 3A-3D. In FIG. 3A, a sample signal produced by thecontrol unit is shown (x-axis is time, y-axis is voltage, not to scale).This is one example of an asymmetric, biphasic square wave commonly usedin NMES. In FIG. 3B, an example signal that can be measured just outsidethe region of stimulation (in the area marked as (1) in FIG. 3E) isshown. The overall energy amplitude is lower (not to scale), and theshape is somewhat different than the original signal shown in FIG. 3A.However, the pulse width and the polarity may be similar. In FIG. 3C, anexample signal measured in a location even more remote from the NMESsite (region (2) of FIG. 3E) is shown. Though the same shape and pulsewidth as the signal shown in FIG. 3B, this signal measured more remotefrom the region of stimulation has relatively lower amplitude.

One embodiment of the presently-disclosed devices, systems and methodsoperates by producing the inverted version of the signal shown in FIG.3C and delivering it to the body at an appropriate location (forexample, near region (2) of FIG. 3E). We refer to this inverted signalas the counter signal, an example of which is shown in FIG. 3D. Byproducing an opposite polarity but equal amplitude counter signal usingcounter signal electrodes (303), it is possible to cancel out theinterference signal originating from the stimulation region (region ofelectrodes (302)) and prevent it from spreading into more distalregions. Counter signal characteristics may be matched so that thepropagation characteristics of the counter signal are similar to thoseof the NMES interference signal, allowing for the impact of theinterference signal to be minimized over considerable distances.

The amplitude of the counter signal is important to note. As describedabove, to be practical any counter signal needs to minimize the effectof the NMES interference signal on remote monitoring and/or sensingdevices, but also not meaningfully impact the effectiveness of the NMESitself. Since in general counter signals are required to be ofrelatively small amplitude (especially relative to stimulation signals,for example that shown FIG. 3A), they do not significantly interact withmuscles or cancel out the electrical current that needs to be depositedin the muscle region in order to provide suitable NMES therapy.

Preferable embodiments will use fixed positions of the stimulationelectrodes and counter-signal producing electrodes. As such, empiricalinformation may be used to determine a priori the most suitable countersignal for the control unit to deliver in order to most effectivelycancel the NMES interference signal in remote regions. In variousembodiments, this counter signal may be static, may be adjusted asneeded based upon adjustments (ex. intensity, pulse width) to the signalbeing delivered to the stimulation electrodes for NMES, and/or may becalculated based on local factors such as control unit-measuredimpedance between either or both sets of electrodes. In someembodiments, the counter signal may be adjusted or fine-tuned manuallyby an operator, for example by an operator who is observing an ECGmonitor and may adjust the counter signal such that use of the NMESdevice produces the least amount of interference.

In variations of the preferable embodiments, sensor systems may be usedto measure the interference signal as it travels away from the regionbeing treated with NMES. In these embodiments, one or more sensors canbe utilized to help the control unit produce the most effective countersignal possible. Sensors may be utilized in a number of ways. In someembodiments, the sensors may be positioned to measure the interferencesignal (as in FIG. 4A), which can then be inverted and possibly scaledto produce a counter signal. In variation implementations, a sensorcould be placed in a region distal to the electrodes used to deliver thecounter signal (for example, as shown in FIG. 4C), and thus bepositioned to measure any residual signal. Some implementations may usemultiple sensors in one or both of these positions, or in otherpositions that will be clear to those skilled in the art. Depending onthe embodiment, sensors may be built into a pad with the electrodes(fixing their relative positions), or may be placed discretely on thesubject without the use of a pad. In some embodiments, multiple pads maybe utilized to optimize the position of sensors and electrodes.Depending on the body part receiving NMES and the relative position ofthe monitoring equipment and/or device sensors where interference isintended to be minimized, sensors and counter signal electrodes may beplaced in close proximity to the stimulation region (for example, as inFIG. 4B) or more remotely from the stimulation region (as in FIG. 4E).

In some embodiments it may be desirable to minimize interference withmore than one electrical sensor remote from the NMES site. For example,when using NMES in the presence of ECG monitoring, which requiresmultiple electrodes. In this situation, some embodiments may use simpleconfigurations of counter signal producing electrodes (ex. FIG. 5A),while other embodiments will implement more advanced active cancellationtechniques that account for different path lengths and directionality ofthe interference signal as it spreads away from the region of NMES. Anexample configuration of a more advanced active cancellation system(control unit not shown) is shown in FIG. 5B.

In a preferable embodiment of the method described herein, one stepwould involve placing at least one stimulation electrode and at leastone counter-signal producing electrode on the body of a subject. A laterstep would be applying stimulation energy to a body region of a subject,with sufficient enough amplitude to produce a muscle contraction. Asimultaneous (or slightly later, depending on the configuration) step inthe method is to apply a second active signal to the body, in the formof a counter signal, said counter signal having an appropriate shape,polarity, amplitude, and anatomical origin to effectively minimize oreliminate the interference the first stimulation energy signal producesin electrical measurements captured by sensors remote to the NMESregion. In some embodiments of the method, an additional step involvesusing a sensor to estimate either the interference signal, the residualsignal resulting after the counter signal is applied, or both, andadjusting the counter and/or NMES signal properties accordingly in orderto minimize electrical interference with remote monitoring equipmentand/or devices that require electrical sensing to function properly. Anexample embodiment of the method is shown in FIG. 6 .

DESCRIPTION OF THE DRAWINGS

While preferable embodiments of the invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention.

As shown in FIGS. 1A-1B, example preferable embodiments of thepresently-disclosed devices and systems. In FIG. 1A, control unit 101contains an LCD touchscreen display/user interface as well as a numberof controls, knobs, buttons, and dials. An interconnect cable 102connects the control unit to pads 103 that contain both stimulation andcounter signal electrodes. In FIG. 1B, the subject-contacting side ofpad 103 is shown, with an example configuration of stimulation 104 andcounter signal producing 105 electrodes.

As shown in FIGS. 2A-2D, variations of preferable embodiments of thedevices and systems that include electrodes used to deliver N ES andelectrodes used to produce a counter signal. In FIG. 2A, a subject 201is being monitored with four ECG electrodes 204 on his torso. A controlunit 202 is connected to a pad 203 configured to provide NMES andcounter signals to the leg. In FIG. 2B, the pad 203 is configured sothat counter signal electrodes 205 are located between stimulationelectrodes 2044 and ECG monitoring sensor electrodes 204 (not shown inthe FIG. 2B) when pad 203 is placed on the subject as shown in FIG. 2A.In FIG. 2C, shown is a different shaped pad 206 configured for anotherbody part of the subject. In the embodiment shown, a different relativeposition of the counter signal electrodes 205 and stimulation electrodes2044 is implemented. In FIG. 2D, an embodiment that does not use a padand instead uses discrete individual electrodes that can be placed onthe subject in positions that the NMES operator deems appropriate isshown.

As shown in FIGS. 3A-3D various electrical signals associated with thedevices, systems, and methods described herein. The y-axis representsrelative voltage (not to scale) and the x-axis represents time (not toscale). All signals shown are approximate and for the purpose of exampleonly. Please refer to FIG. 3E for clarification as the signals in FIGS.3A-3D are described. In FIG. 3A, an example signal that a control unit301 may provide to stimulation electrodes 302. In FIG. 3B, an examplesignal that could be measured outside of the region of stimulation atlocation (1). In FIG. 3C, a relatively smaller amplitude signal thatcould be measured further outside the region of stimulation at location(2). The signals shown in FIG. 3B and FIG. 3C are the interferencesignal that is produced as a byproduct of NMES signal FIG. 3A beingapplied in the intended region of stimulation. In FIG. 3D, an examplecounter signal with similar amplitude but opposite polarity of theinterference signal shown in FIG. 3C, which can be applied at countersignal electrodes 303 to cancel out the interference signal and thusminimize the impact it could have on monitoring sensors and/or deviceslocated more remotely to the region of NMES. In FIG. 3E, an examplesystem configuration, as well as annotated regions (1) and (2) thatcorrespond to the signals shown in FIG. 3B and FIG. 3C, respectively.

As shown in FIGS. 4A-4E, variations of preferable embodiments of thedevices and systems that include electrodes used to deliver NMES andelectrodes used to produce a counter signal as well as sensors used inconjunction with the system. In FIG. 4A, a system pad 401 contains asensor 403 that is located between stimulation electrodes 402 andcounter signal electrodes 404. In FIG. 4B, a variation embodiment thatuses multiple sensors 403. In FIG. 4C, a further variation embodimentwhere the sensor 403 is positioned relatively further away from the zoneof stimulation compared to the location of the counter signal electrodes404. In FIG. 4D, an embodiment that uses two system pads, a primary pad401 that contains stimulation electrodes 402 and a secondary pad 405that contains both a sensor 403 and a monopolar counter signal electrode404. In FIG. 4E, an embodiment of the systems and devices configured foruse on the arm of a subject. Both the sensors 403 and the counter signalelectrodes 404 are located in a position remote from the zone ofstimulation.

As shown in FIGS. 5A-5B, variation embodiments of the devices and systemshown in multiple configurations. In FIG. 5A, a system pad 502 is placedon a subject's leg, with counter signal producing sensors 503 located onthe system pad in a region proximal to the zone of NMES but remote fromthe ECG sensors 501. A variation embodiment is shown in FIG. 5B, wherepad 502 contains only stimulation electrodes, and counter signalproducing electrodes 503 are positioned relatively more remotely fromthe NMES site, closer to the monitoring sensors where it is desired tominimize any interference signal originating from the stimulation zone.In FIG. 5B, several sets of counter signal producing electrodes are usedto account for various directionality aspects of the interference signalas it travels to different ECG sensors 501.

As shown in FIG. 6 , steps in one preferable embodiment of the methoddescribed herein. Shown are several example steps in a preferableembodiment of the method disclosed. Variations of this preferable methodmay skip the sensing step (b), relying on operator-set,internally-calculated, or pre-determined settings for the countersignal.

What is claimed is:
 1. A method of reducing stimulation signalinterference with an electrical monitoring device, comprising: sensingan electrical interference signal at a first location in a bodyresulting from delivery of an electrical muscle stimulation signal at asecond location in the body; and delivering an electrical counter signalto the patient that destructively interferes with the electricalinterference signal to prevent interference with the electricalmonitoring device.
 2. The method of claim 1, wherein the electricalmonitoring device is one of a pacemaker, defibrillator, or a sensingelectrode of a monitoring system.
 3. The method of claim 1, wherein thefirst location and the second location are local to one another.
 4. Themethod of claim 1, wherein the first location and the second locationare remote from one another.
 5. The method of claim 1, wherein theelectrical monitoring device is at a third location, separate from thefirst and the second locations such that the electrical counter signaldestructively interferes with the electrical interference signal beforeit reaches the electrical monitoring device.
 6. The method of claim 1,wherein the electrical counter signal is delivered by an externalelectrode that is configured to be moveable to different locations onthe body.
 7. The method of claim 1, wherein the electrical interferencesignal is sensed by a sensor configured to be secured to the body. 8.The method of claim 1, wherein the electrical muscle stimulation signalis delivered by a first independent energy delivery channel of a musclestimulation system and the electrical interference signal is deliveredby a second independent energy delivery channel of the musclestimulation system.
 9. The method of claim 1, wherein the electricalcounter signal is adapted such that it does not degrade the stimulatingeffect of the electrical muscle stimulation signal.
 10. The method ofclaim 1, wherein the electrical counter signal has an amplitude and aphase such that, at the location of the monitoring device, theelectrical interference signal is eliminated or minimized.
 11. A musclestimulation system configured to reduce stimulation signal interferencewith an electrical monitoring device, comprising: a sensor configured tosense an electrical interference signal at a first location in a bodyresulting from delivery of an electrical muscle stimulation signal by astimulation electrode at a second location in the body; and a countersignal electrode configured deliver an electrical counter signal to thepatient that destructively interferes with the electrical interferencesignal, to prevent interference with the electrical monitoring device.12. The system of claim 11, wherein the electrical monitoring device isone of a pacemaker, defibrillator, or a sensing electrode of amonitoring system.
 13. The system of claim 11, wherein the stimulationelectrode and the counter signal electrode are positioned on anelectrode pad.
 14. The system of claim 11, wherein the stimulationelectrode and the counter signal electrode are separate from andpositioned remote from one another.
 15. The system of claim 11, whereinthe electrical monitoring device is at a third location, separate fromthe first and the second locations such that the electrical countersignal destructively interferes with the electrical interference signalbefore it reaches the electrical monitoring device.
 16. The system ofclaim 11, wherein the counter signal electrode is configured to bemoveable to different locations on the body.
 17. The system of claim 11,further comprising a first independent energy delivery channel fordelivering the electrical muscle stimulation signal and a secondindependent energy delivery channel for delivering the electricalinterference signal.
 18. The system of claim 11, further comprising acontroller adapted to vary the electrical counter signal based on theelectrical interference signal.
 19. The system of claim 11, wherein theelectrical counter signal is adapted such that it does not degrade thestimulating effect of the electrical muscle stimulation signal.
 20. Thesystem of claim 11, wherein the electrical counter signal has anamplitude and a phase such that, at the location of the monitoringdevice, the electrical interference signal is eliminated or minimized.